Well, I tried with a fresh copy of Xampp 1.6.7 (no installer, zip version), and used the zip version of Tomcat addon. The batch file used to start Tomcat close itself aftear reaching the last instruction... and Tomcat doesn't start.

So I tried with a fresh version of Xampp 1.6.6a, and I didn't have any luck, until I decided to use dtx.exe to start Xampp. Now Tomcat (for Xampp 1.6.6a) runs, but it says "The Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path". But at least it is running, however, I don't know if I am doing something wrong, or if there is a bug in version 1.6.7. Of course, I tried to use dtx.exe with xampp 1.6.7, since that solved the problem in 1.6.6a, but it didn't solve the problem...